土壤分形结构对其水力性质的指示作用

研究土壤的水力性质是进行生态水文模拟、农业水分管理和环境监测的关键,然而强烈的空间变异造成土壤的物性特征异常复杂,特别是水力性质测定困难,试验结果随机性强,耗费大量人力物力,却难以准确描述。本文在综合分析了国内外30余种量化土壤水力性质的研究方法的优劣后,系统总结了分形理论在土壤物性特征研究中的应用,剖析了分形理论与土壤水力性质之间的关系,旨在探讨土壤分形结构在水力性质领域的发展前景,以及在测定水力特性参数时所具备的优势。结果表明：(1)采用分形方法定量研究土壤结构具备可行性;(2)分形结构方法能够指示水力性质,并能为快速准确刻画不同尺度下的土壤水分分布特征提供科学依据;(3)利用已知土壤水力性质建立分形模型可以有效反演土壤结构。     

Numerical simulation on the influences of Wenchuan earthquake on the surrounding faults

On 12 May 2008, the devastating Wenchuan earthquake struck the Longmenshan fault zone, which comprised the eastern margin of the Tibetan Plateau, and this fault zone was predominantly a convergent boundary with a right-lateral strike-slip component. After such a large-magnitude earthquake, it was crucial to analyze the influences of the earthquake on the surrounding faults and the potential seismic activity. In this paper, a complex viscoelastic model of western Sichuan and eastern Tibet regions was constructed including the topography. Based on the findings of co-seismic static slip distribution, we calculated the stress change caused by the Wenchuan earthquake with the post-seismic relaxation into consideration. Our preliminary results indicated that: (1) The tectonic stressing rate was relatively high in Kunlun mountain pass-Jiangcuo, Ganzi-Yushu, Xianshuihe and Zemuhe faults; while in the east Kunlun and Longriba was medium; also the value was less in the Minjiang, Longmenshan, Anninghe and Huya faults. As to the Longmenshan fault, the value was 0.28×10^-3 MPa/a to 0.35×10^-3 MPa/a, which is coincident with the previous long recurrence interval of Wenchuan earthquake; (2) The Wenchuan earthquake not only caused the Coulomb stress decrease in the source region, but also the stress increase in the two terminals, especially the northeastern segment, which is comparatively consistent with the aftershock distribution. Meanwhile, the high concentration areas of the static slip distribution were corresponding to the Coulomb stress reductions; (3) The Coulomb stress change caused by Wenchuan earthquake showed significant increase on five major faults, which were northwestern segment of Xianshuihe fault, eastern Kunlun fault, Longriba fault, Minjiang fault and Huya fault respectively; also the Coulomb stress on the fault plane of the Yushu earthquake was faintly increased; (4) We defined the recurrence interval as the time needed to accumulate the magnitude of the stress drop, and the recurrence interval of Wenchuan earthquake was estimated about 1 714 a to 2 143 a correspondingly.     

Microtremor study of site effects and soil-structure resonance in the city of Ljubljana (central Slovenia)

The city of Ljubljana is located in one of the three areas with the highest seismic hazard in Slovenia, and it is also the most densely populated. Site effects due to Quaternary sediments, which fill the up to 200 m-deep basin, are characteristic of the whole city area, but they can be especially strong in the southern part of Ljubljana, which is built on very soft lacustrine deposits. Existing microzonation studies of the city are inadequate, since there is a lack of borehole, geophysical and earthquake data. The microtremor horizontal-to-vertical spectral ratio (HVSR) method was therefore applied to a 200 m dense grid of free-field measurements over an area of 45 km² (1,223 measuring points) in order to assess the fundamental frequency of the sediments. The main difficulties in microtremor measurement arose from high levels of traffic and industrial noise, and from underground structures. Experimental conditions which can influence data quality, such as strong wind and water saturation of soil, were analysed. Very clear HVSR peaks were obtained in the entire southern part of the city, whereas in the northern part the site response is in general lower due to lower impedance contrast of gravel with the bedrock. The iso-frequency map of sediments shows a distribution in the range of 0.9–10 Hz. In the southern part of Ljubljana, sediment frequency correlates well with the thickness of soft sediments known from geophysical investigations and sparse drilling. Average amplitude of the HVSR peaks is considerably higher in the southern part (6.7 ± 2.4) than in the northern part (4.0 ± 2.0) of the city, indicating a high impedance contrast of lacustrine sediments with the bedrock. Microtremor measurements were also performed inside 122 buildings of various heights. We focused on important public buildings and selected blocks of flats and houses. To assess the longitudinal and transverse fundamental frequencies of each building, amplitude spectra and the spectral ratio between the upper floor and the basement were analysed for both directions. When one of these frequencies is close to a nearby free-field fundamental frequency, a potential soil-structure resonance is present. This was found in 12 of the measured buildings. Three of them are tall residential buildings (from 10 to 15 floors) with a fundamental frequency of 2–3 Hz, and nine of them are low-rise buildings (from 3 to 5 floors) with a fundamental frequency ranging from 3 to 4.5 Hz. Using the relationship between fundamental frequency and height, the typical height of buildings that might cause soil-structure resonance can be estimated at a given sediment frequency obtained from free-field measurements.     

Impact of the dam water discharge on the circulation system in the Kangjin Bay,South Sea,Korea

This study is based on a series of numerical modeling experiments to understand the impact of the Namgang Dam water discharge into the Kangjin Bay (KB). Numerical model performances were tested in terms of various skill analyses, with skill scores for elevation and tidal current over 85 %. The models successfully reproduced the tidal circulation and the response of fresh water input and subsequent dilution of salinity field. The behavior of the fresh water plume in the KB was investigated and analyzed. The different pattern of densitydriven current field was described at tidal phases. The modified tidal ellipse characteristics are estimated as a result of interaction between tidal current and density current.     

浓雾——隐形的气象杀手

1 雾的危害 2007年5月,京珠高速公路614公里处河南新乡段因浓雾突发,连续发生多起追尾事故,百余辆车相撞,事件过程中,200余人参加了事故大营救.     

太原市灰霾期间黑碳气溶胶形貌与成分分析

为掌握太原市冬季灰霾发生期间黑碳气溶胶形貌特征和化学成分变化特点,分别于2011-12-30 T 08:00至2012-01-01 T 04:00和2018-11-25 T 08:00至2018-11-27 T 04:00灰霾发生期间在山西大学环境与资源学院楼顶使用MAY七级冲击式颗粒采样器每隔4 h采集空气动力学直径...     

The impact of heat waves on surface urban heat island and local economy in Cluj-Napoca city,Romania

The association between heat waves and the urban heat island effect can increase the impact on environment and society inducing biophysical hazards. Heat stress and their associated public health problems are among the most frequent. This paper explores the heat waves impact on surface urban heat island and on the local economy loss during three heat periods in Cluj-Napoca city in the summer of 2015. The heat wave events were identified based on daily maximum temperature, and they were divided into three classes considering the intensity threshold: moderate heat waves (daily maximum temperature exceeding the 90th percentile), severe heat waves (daily maximum temperature over the 95th percentile), and extremely severe heat waves (daily maximum temperature exceeding the 98th percentile). The minimum length of an event was of minimum three consecutive days. The surface urban heat island was detected based on land surface temperature derived from Landsat 8 thermal infrared data, while the economic impact was estimated based on data on work force structure and work productivity in Cluj-Napoca derived from the data released by Eurostat, National Bank of Romania, and National Institute of Statistics. The results indicate that the intensity and spatial extension of surface urban heat island could be governed by the magnitude of the heat wave event, but due to the low number of satellite images available, we should consider this information only as preliminary results. Thermal infrared remote sensing has proven to be a very efficient method to study surface urban heat island, due to the fact that the synoptic conditions associated with heat wave events usually favor cloud free image. The resolution of the OLI_TIRS sensor provided good results for a mid-extension city, but the low revisiting time is still a drawback. The potential economic loss was calculated for the working days during heat waves and the estimated loss reached more than 2.5 mil. EUR for each heat wave day at city scale, cumulating more than 38 mil. EUR for the three cases considered.     

天山山区与南北疆夏季温度变化对比分析

利用新疆1959～2000年夏季温度资料,采用滑动平均、最大熵谱、经验正交、线性回归方法,分析天山山区近42年来夏季温度变化的基本特征,并与南疆、北疆进行比较。结果表明：①天山山区在夏季温度的冷暖变化阶段以及最炎热、最凉爽年出现的年份与南疆和北疆不同;②夏季温度空间分布的同向性变化北疆最大,天山山区居中,南疆最小;夏季温度空间反向变化南疆和天山山区较大,北疆较小;③夏季温度的年代际变化趋势不同,天山山区持续增温,北疆波动增温,南疆变化稳定;④三种夏季增温的覆盖范围以最低温度为最广,其增温率天山山区最大,南疆最小,北疆居中。     

Phenological observations made by the I. R. Bohemian Patriotic�CEconomic Society, 1828�C1847

Drought forecasting is a critical component of drought risk management. Identification of effective predictors is a major component of forecasting models. Sea surface temperature (SST) and sea level pressure (SLP) are relevant predictors for short- to long-term drought forecasts. However, these datasets are captured globally within a cell-wise network. This paper describes an approach to locate the most effective cells of the SST and SLP datasets using data mining. They are then applied as input to an adaptive neurofuzzy inference system (ANFIS) model to forecast possible droughts 3, 6, and 9?months in advance. Tehran plain was selected as the study area, and drought events are designated using the effective drought index (EDI). In another treatment, past values of the EDI time series were introduced to the ANFIS and the results compared with the previous findings. It was shown that R ² values were higher for all cases applying the SST/SLP datasets. Additionally, the performance of SST/SLP datasets and the ANFIS model was assessed according to ??drought?? or ??wet?? classification, and it was concluded that more than 90% of the time the ANFIS model detected the drought status correctly or with only a one class error.